The invention relates to a palletizing for displaying stackable objects, particularly printed products arranged in stacks. The palletizing robot includes a gripping device arranged on an arm that is driven so as to be rotatable about a vertical axis. A horizontally oriented transverse member is provided which includes a track along which the rotatably mounted arm is guided so as to be displaceable along the transverse member. The gripping device is also rotatable about a vertical axis, and a portion of the arm extending in the horizontal direction is disposed below the transverse member.
A palletizing robot for lifting a stack of material from a support, particularly a stack of cut pieces from an intermediate support or a bottom support for use in the tobacco industry is disclosed in German Published Application 3,718,601. The palletizing robot includes a horizontally oriented transverse member including a track provided, by way of an intermediate element, with an arm that is rotatable about a vertically oriented axis and is equipped with a gripping device which is driven to be likewise rotatable about such an axis. A bearing means carries the intermediate element and the arm with the gripping device. This ensures, on the one hand, guidance along the transverse member and, on the other hand, rotation of the arm below the transverse member. The bearing means and the horizontally oriented arm are connected by way of the intermediate element and are each mounted so as to be movable about horizontally oriented axes at the points where they are connected with the intermediate element. The gripper is movable along one translatory axis and about three rotation axes.
The prior art palletizing robot has the drawback that, during the palletizing process, the gripping device is moved about four axes (according to definitions applicable for robot systems). This requires high expenditures for controls and construction and a complicated drive. Moreover, the operating speed of the robot is very slow and therefore the turnover times at the palletizing stations are correspondingly long. Although the palletizing robot is able to compensate for the increasing height of the depositing surface during a stacking palletizing process, the kinematics provided for this purpose make it very slow. This drawback can be overcome according to the prior art only by means of cost intensive measures, such as providing an additional palletizing station or installing accumulation surfaces in the processing or transporting line for the material to be palletized. Moreover, the palletizing robot is weight intensive and is thus subject to great stresses in its joints during the palletizing process. With the desired high operating velocity this leads to an equivalent degree of an increase in susceptibility to malfunction of the palletizing robot. High maintenance costs must therefore be accepted in connection with the prior art palletizing robot.
Furthermore, German Democratic Republic Patent 2,226,267 discloses a device for the manually guided displacement of stackable objects. In this case, a horizontally extendable arm which is rotatable about a vertically oriented axis is articulated by way of a bearing means to a horizontal transverse member. The bearing means is configured so as to be movable in the horizontal direction along the transverse member. The free end of the rotatably mounted arm is further provided with a vertically downwardly extendable lifting element, with a gripping device being mounted to its end so as to be rotatable about a vertically oriented axis. As a whole, the gripping device is thus manually movable along three translatory axes and about two rotation axes.
The device for the manually guided displacement of stackable packets has the drawback that it is unsuitable for automatic palletizing. Manual displacement of the stacks with this device, on the one hand, is too slow and, on the other hand, too wage intensive. Even if it were possible to retrofit this structure for automatic displacement, its drawbacks, such as excess weight of the moving parts and complicated kinematics, would also affect the above-mentioned palletizing robot.
It is the object of the invention to provide, in a palletizing robot of the above-mentioned type, a structure which, with a simplified configuration, permits faster operation while eliminating the above-mentioned drawbacks.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the palletizing robot includes a substantially horizontal transverse member; a track disposed on and extending along the transverse member; a support bearing slidably disposed on the track; an arm having a first end rotatably attached to the bearing for rotation about a substantially vertical axis, and a second end vertically spaced below the transverse member; a gripping device which is designed for grasping stacked objects and which is pivotally attached to the second end of the arm for rotation about a substantially vertical axis; a guide extending vertically downwardly from the second end of the arm for guiding the gripping device for vertical displacement thereon towards and away from the second end; and a drive for vertically displacing the gripping device on the guide by a predetermined amount.
The invention is based on the realization that, for palletizing or depalletizing of stackable objects, it is possible to significantly increase the palletizing speed by a structure having the least possible number of active joints within the palletizing robot, while retaining a large access range for the robot.
Joints require precise drives and accurately defined arresting positions. In the solution according to the invention, joints that permit bending of the arm have intentionally been avoided. Instead, the arm is made rigid and preferably has a box-shaped aluminum profile.
The sole rotary joint of the rigid arm which rotates about a vertical axis, together with the horizontal displaceability of the rotatably mounted end, permits quick and precise movement of the gripping device over a large operating range. In order to compensate for the different depositing and receiving surfaces created during palletizing or depalletizing by warping or tolerances in the stack heights, the gripping device is configured to be displaceable by a vertical lifting movement of a few centimeters. This lifting movement is realized by a simple vertical auxiliary guide for the gripping device in the gripping arm. The gripping device is shiftable to a fixed extent. Due to its small range of movement, the vertical compensatory movement of the gripping device does not interfere with the high palletizing speed realized by configuring the robot with few joints. Moreover, palletizing and depalletizing always takes place within the same stacking plane, with raising or lowering of the pallet by one stack position at a time taking place after the respective loading or unloading process.
The adjustment range for conveyors and conveying means remains advantageously provided by the transverse member structure. For transporting processes in connection with pallets, it is necessary to be able to operate over the adjustment range of the pallet itself as well as over a feeding or removal range for the material to be stacked and for corresponding devices. The surfaces to be loaded in each case usually have a basically rectangular shape and, for reasons of saving space, are arranged next to one another. Applicable in this connection are, in particular, conveyor belts or processing machines which receive or discharge the conveyed material.
The robot according to the invention, is thus particularly adapted to the palletizing conditions due to its kinematics and particularly also because of the longitudinally displaceable arrangement of the rotatable gripping arm at the transverse member which makes it possible to operate over a broad area. The entire region below the transverse member is available for access. The length of the arm need not be changed since every point within an oval access range can be reached by a different angular position of the arm relative to the transverse member. Within the access range, no zones are left open which could not be adjusted by the robot itself or could not be reached by the gripping arm. The important factor is also that all points of the access region (except for the outermost edge region) are accessible from any direction. This is connected with the advantage that no restrictions exist for loading or unloading of stacks. Particularly in cramped conditions or in connection with special requirements for the insertion or removal direction for the material being transported, multitudinous demands can be met.
The loading and unloading stations may be arranged in any desired juxtaposition so that, due to the short times involved, the transporting times can be further reduced considerably and thus the efficiency of the transporting system is increased compared to similar systems.
The device according to the invention is particularly suitable for the transport of printed products in a collecting folder or in the form of loose or bound-together stacks. In the field of magazine production, all transporting processes around the printing presses and the shipping department can be automated. This includes, in particular, the combination of individual, separately produced parts to be stapled together and the assembly of bundles for shipping. In the combination of parts that were printed at an earlier time with up-to-date portions that are to be included, it is possible to produce a time "buffer" within the production line by supplying a region designated for storage.
In particular, the following advantageous modifications are favorable:
An even larger operating range can be realized if the transverse member is provided with a horizontally displaceable support.
Moreover, in a further embodiment according to the invention, the access times are shortened, in particular, if the rotation angles of gripper arm and/or gripping device are more than 360.degree., since in that case, successive transporting movements can usually be performed without a complete return rotation as it would otherwise be necessary if a final stop were reached prematurely.
Due to the provision of several parallel tracks on a transverse member, the use of several gripper arms that are controlled in a coordinated manner permits further reduction of turnover times. In this connection, a control unit is preferably provided which blocks coinciding overlaps between gripping regions.
In a preferred embodiment for the stacking of packets of printed products by the palletizing robot, the differences in height caused by the stacking are compensated by platforms, such as lifting tables, which can be raised and lowered so that there is a division of the directions of movement, i.e. the horizontal and vertical movements, between the lifting table and the robot during palletizing and depalletizing. While the palletizing robot palletizes continuously according to a predetermined scheme, the lifting table is lowered by the height of a stack as soon as a layer of stacks has been palletized. Thus, the robot is able to perform the palletizing as quickly as possible with minimum movements. The depalletizing process takes place in a correspondingly reversed direction and sequence. With an average angular movement of the gripping arm, the process from gripping a stack until depositing it takes 1.5 seconds; with the prior art robots, however, it takes 5 seconds. The saving in time has become possible by distributing the tasks of the horizontal and vertical movements to two devices and by the simplified kinematics. Therefore, the control system configuration for the palletizing robot is simplified considerably compared to the prior art embodiments. The lifting table is lowered whenever light barriers which are in operative communication with the lifting table and the packets to be stacked send a signal to the control unit.
It has been found to be particularly favorable for the moving parts of the robot to be made of aluminum and of a light-weight construction. This reduces the mass to be moved and thus the robot's susceptibility to malfunction.
Controlling the palletizing robot according to the invention is enhanced in that a buffer memory of the type of a shift register is provided whose memory locations store movements that are to be performed in succession. If a coinciding overlap of gripping regions occurs and a gripping arm is blocked, the blocked gripping arm is given a task which is scheduled to be performed later. This task is placed ahead in sequence in the buffer memory and is thus performed earlier. Preferably, the individual memory locations are provided with additional identifications regarding the time duration and/or association with individual gripping arms of the movements to be performed.
By means of a control device which includes a memory for different predetermined palletizing schemes, different transporting processes can be performed quickly and flexibly according to a respectively predetermined scheme.